I shaved the pubes around it and then played around with camera angles (this is all with my own dick, for clarification). Like with physique, lighting/angles/poses/etc will make a big difference. Also, if you have big hands/legs then it'll look comparatively smaller than for a shorter/smaller guy with an average D. Also, could be some problems with the qualities of the erection, not getting maximal blood flow due to stress or whatever. You might be able to find configurations of these factors that will make it look like your D is actually fairly big, with an average size penith. Think I'm also around average, but I've literally thought my D looked big several times just by doing these things (biggest factors are shaving pubes and having good blood flow). Sometimes it'll look bigger when not fully erect, as well. It's basically akin to rocket science in terms of how complicated it actually is, imo. Can't compare ourselves to pics online and stuff, either (some guys have very big penises, but it's not super relevant to our lives, and it does literally only come down to two or three inches, plus or minus), and even then there's a lot of movie magic involved (a D will look bigger if a small woman is grabbing it than if u grab it with your man-hands).
About the gf stuff, I think people underestimate just how chaotic all that is. I am autistic/NEET/etc, and so are many other MWWTHARBDHOs (men who want to have a relationship but don't have one). We also often lack the anecdotal data that's out there for people who socialize. This means that when trying to figure out why some people have girlfriends and some don't there's an increased risk of black-and-white-thinking/overgeneralizations. There are of course trends, and some things that are more or less nailed down at this point (in terms of trends/statistics), but I think generally speaking there's a huge chaos factor that accounts for a big part of things. Basically, "everything can happen" and "it's never too late" and "there's someone for everyone" has some grain of truth to it.
The things that might actually prevent you from getting a gf seem to be these (rather than having an average-sized penis), in no order of importance:
1. Being a NEET.
2. Being autistic.
3. Not having a social life.
4. Having a bad personality (weakness/volatility/pettiness/spitefulness/stupidity/etc).
5. Being physically unattractive.
6. Not having a college degree.
7. Not being confident.
8. Being "boring" and/or "negative".
9. Being "needy".
10. Making less money than her.
11. Living with parents.
12. Dressing poorly.
13. Not driving a car.
14. Not grooming/washing enough.
15. Having fringe religious/political beliefs, unusual moral system, that sort of thing.
16. Not being interested in parties/clubs/gatherings/etc.
17. Being very monogamous, wanting a virgin to marry, stuff like that.
18. Being a "quitter".
19. Rejecting women once you do get a chance due to some psychological problems or whatever (including body dysmorphia).
20. Not really meeting women, even if you have some sort of social life.
And much, much more, I guess. Again, depends on the woman. I've read stories on here that suggest that even suicidally depressed and disabled, sometimes even unhygienic or overweight, women can basically just grab an attractive, popular and successful (often older, as well) guy and suddenly move in with him and get a regular life going; so it's not looking great for those of us that can't provide anything. So it's important to not have to tangle with any body dysmorphia on top of everything else. Not to sound too pessimistic, a relatively normal guy shouldn't have a problem if he meets many women.
Anyway, in my opinion the only problem with your penis size is that it makes you less confident, basically. If you manage to get a girl to want to see that penith, worry about it then rather than now, if at all possible. And great that you think that it's a possibility that someone will eventually have sex with you, it's way more hope than I have, but I'm personally more or less checking all of those 20 points, heh.